The present invention relates to motor control, and specifically to an automatic control switch for an electric motor.
Electric motors are often employed in situations where they are run semi-continuously, such as during daylight hours only. In other situations, a two-speed motor may be run at one speed during the day and at a lower speed at night. For example, in the context of an outdoor pool, the pool pump employs a fractional horsepower AC motor. The pool pump is typically run at high-speed during the day since the pool is in use during the day and incident sunlight upon the water encourages algae formation within the pool. It is less important to operate the pool during the night. Accordingly, it may be desirable to run the pump at low speed or not at all during the night so as to conserve energy and prolong the life of the motor.
There are other circumstances in which it is desirable to automatically control the operation of a motor based upon external environmental criteria. These criteria may include temperature, fluid level, pressure, or other measurable parameters.
A conventional approach to motor control has been to employ mechanical timers. A drawback of mechanical systems for switching a motor on an off is the fallibility of moving components and the extra cost and complexity associated with such systems. A timer approach also relies upon a user to set an appropriate time using the mechanical device. Other approaches to motor control have met with limited success, but are often excessively complex.
Another drawback to known systems that incorporate a motor controller having a daylight sensor is that the pool motor is often housed within a pool shed rendering it impracticable to sense daylight at the motor location.
The present invention provides a simple and economical mechanism providing automatic motor control.
In one aspect, the present invention provides an enclosure that houses a sensing device and motor-rated relay. The motor-rated relay is directly connected to line voltage and directly connected to input terminals for powering the motor. The relay is also connected to the sensing device for receiving a signal that triggers the relay to turn on or off.
In another aspect, the present invention provides a mechanism that includes a connection enclosure and a separate sensing device enclosure, the two enclosures being connected by a cable. The connection enclosure includes a motor-rated relay for direct connection to input line voltage and directly connected to input terminals for powering the motor. The relay is also directly connected to the cable for receiving a signal from a sensing device located within the sensing enclosure.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.